Automobiles and various other vehicles include braking systems for reducing vehicle speed or bringing the vehicle to a stop. Such braking systems generally include a controller that regulates the delivery of braking pressure to braking calipers on one or both axles of the vehicle to produce braking torque for the vehicle.
Various vehicles, such as certain fuel cell, electric, and hybrid electric vehicles, utilize regenerative braking in addition to friction braking. While such vehicles typically have front and rear friction brake calipers in addition to regenerative braking, some fuel cell, electric, and hybrid electric vehicles may have friction brake calipers only on a single axle, and thus may rely solely on regenerative braking on the other axle. Such a case may include, without limitation, a vehicle having four wheel motors that are situated on the vehicle so as to provide propulsion and braking at the four corners of the vehicle.
Thus, certain fuel cell, electric, or hybrid electric vehicles may have friction braking that is limited to one axle, and regenerative braking that is available on both axles. During regenerative braking, electrical energy is generated and stored in an energy storage system. However, in certain situations, the energy storage system may be offline and/or may be otherwise unable to accept additional electrical energy.
Accordingly, it is desirable to provide an improved method and system for controlling braking in a vehicle, such as a fuel cell, electric, or hybrid electric vehicle, that can be used when the energy storage system of the vehicle cannot accept additional electrical energy, for example to allow braking on an axle that is not equipped with friction brakes. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.